Precursor cells specific to sheep red cells in nude mice. estimation of frequency in the microculture system

Abstract A dilution scheme for bone marrow‐derived (B) cells has been applied to estimate the frequency of precursor cells specific to sheep red cells (SRC) present in the spleens of nude mice. B cells were titrated over a range of 0.2 x 10 5 – 1.8 x 10 5 spleen cells of nude mice per microculture in the presence of a constant number of allogeneic spleen cells. Data from 6 limiting dilution experiments are presented. It is argued that only the B cells are being diluted out. The frequency of precursor cells specific for SRC was calculated by means of Poisson statistics. The estimates of these frequencies are in the range 0.9 x 10 ‐5 – 2 x 10 ‐5 .